Support system

ABSTRACT

A support arm system for a load such as a display device. The system includes a support arm ( 4 ) rotatable at its proximal end about a mid-joint axis X″, monitor supporting head ( 5 ) at the distal end of the support arm ( 4 ) has an internal slider element and compression spring, and an arrangement of links and pivots which create a torque to oppose the torque created by a load on the head ( 5 ) and keep a monitor plate ( 6 ) in the same viewing plane relative to the vertical as the arm ( 4 ) moves through its range of movement.

This application is the National Stage of International ApplicationPCT/GB2011/000874, filed Jun. 9, 2011, which was a continuation-in-partof U.S. patent application Ser. No. 13/024,685, filed Feb. 10, 2011, theentire disclosure of which is hereby incorporated herein by reference.

The present invention is concerned with a support system. Particularembodiments of the invention are concerned with a moveable support armfor a monitor or display device.

Modern screen-based display devices are typically flat-screen monitorssuch as liquid crystal display (LCD) or plasma screen displays. Suchdevices can be mounted on elevated support devices such as a support armwhich can then be secured to a surface such that the flat-screen monitoris held above or in front of the surface.

Support systems for monitors are known which allow for movement in threedimensions of the head, mount or bracket on which the monitor ismounted. This is so as to allow for a full range of adjustment of themonitor. GB 2 438 581 and U.S. Pat. No. 7,438,269 both disclose mountsor brackets including an arcuate connection which allows a monitor to bepivoted about a substantially horizontal virtual pivot axis. In U.S.Pat. No. 7,438,260 the virtual pivot axis passes through the centre ofgravity of a monitor or display so as to reduce the forces necessary tohold the mount in place at a selected position on the arcuateconnection.

In order to allow for adjustment about a substantially vertical axis (oran axis orthogonal to the axis of the arcuate connection), knownarrangements such as those disclosed in GB 2 438 581 and U.S. Pat. No.7,438,269 have a second pivoting mechanism entirely separate from thefirst. The second pivot is a separate vertical rod-like element defininga vertical axis. This second pivot is distinct and separated from thepivot of the arcuate connector.

These prior art arrangements require two separate and distinct pivotarrangements. They are therefore relatively complicated and expensive tobuild, have two pivots (and therefore more moving parts) which can failand are relatively unsightly.

The present invention, in its first aspect, provides a single simplemechanism which allows a full range of adjustment of a load in threeorthogonal directions (i.e. about orthogonal X, Y and Z axes). Thismechanism is easier and cheaper to make than the know arrangements andis aesthetically more pleasing.

Support systems for monitors comprising an articulated arm arrangementfor raising and lowering a monitor are known with tiltable mount orbracket mechanisms which keep the monitor in the same plane as the armmoves up and down. The known arrangements such as those disclosed in US2004/0245419 have a four bar linkage or parallelogram arrangement inwhich there is a second link or arm below (or above) and parallel to themain support arm and pivotally coupled to the tiltable mount or bracketon which a monitor is mounted. The second link or arm is pivotallycoupled to the mount or bracket below (or above) the pivot between themain support arm and the mount, and also pivotally coupled to the baseor support element to which the other end of the main support arm ispivotally coupled at a point below (or above) the pivot between the mainsupport arm and the base or support element. The main support arm andthe second link arm are parallel to each other and the linkage (whichcan be considered to be a line drawn between) the pairs of pivots oneach of the base element and mount are also parallel to each other.

This parallelogram four-bar linkage means that as the support arm ismoved up and down the linkage between the two pivots on the tilt mountremains in the same plane parallel to the linkage between the two pivotson the base element.

A disadvantage of the known four-bar parallelogram linkage arrangementsis the need to provide a second link parallel to and separate from thesupport arm. Such arrangements therefore must have a second visible (andtherefore unsightly) link or arm parallel to the main support arm.Alternatively, such parallelogram arrangements have a large deep casingwhich can house the main support arm, the second parallel link and thespace therebetween. This is bulky and therefore also unsightly.

The support system of the present invention in its second aspecteliminates the need for a second parallel link separated from the firstand a vertical separation between the two parallel links. The presentinvention in its second aspect therefore allows for a more compact andaesthetically pleasing support arm which keeps its load mount in thesame plane as the support arm moves up and down.

The use of a slider element moveable along the longitudinal axis of thesupport arm (without a component of movement orthogonal or perpendicularthereto) allows for an aesthetically pleasing structure without a secondvisible arm with a component of movement both along and perpendicular tothe support arm.

A problem with articulated support arms for loads such as monitors ordisplay devices which move up and down as they pivot about a horizontalaxis, is the varying torque created by the constant weight of themonitor applied about the horizontal axis. As the arm moves up and downthe distance from the load at the end of the support arm to the otherend of the support arm and the pivot between the support arm and itsbase varies. The maximum distance and hence torque is when the arm ishorizontal (see FIGS. 12 b and 14 b) and at its minimum when in itsuppermost (see FIGS. 12 a and 14 a) and lowermost (see FIGS. 12 c and 14c) positions.

In order to oppose this varying torque it is known (see, for example, US2004/0245419) to provide a compression spring which provides a variableforce to create a torque to oppose and match the torque created by theweight of the load. The spring is subject to a cam arrangement whichcontrols the degree of compression of the spring and hence the force itapplies.

Cam arrangements of the type disclosed in US 2004/0245419 are relativelycomplex and hence expensive to make.

The present invention in its third aspect provides an arrangement forvarying the torque applied to oppose the variations in torque resultingas the support arm is pivoted about a horizontal axis.

The invention in its third aspect provides a mechanism which allows thevariations in torque provided by the force generating member as thesupport arm pivots and which opposes the weight of a load on the supportarm to better match the variations in torque provided by the weight asthe support arm pivots. The inventors of the subject application are thefirst to realise that taking the step of moving the proximal forcetransmission link pivot away from its usual position on the linevertically through the proximal support arm pivot and substantiallyorthogonal to the longitudinal axis of the support arm when this is atthe mid-point of its range of movement about the proximal support armpivot allows one to better match the shape of the graphs of variation insupporting torque and load weight torque with support arm movement toeach other and hence better support a load on the support arm. Theinventors are the first to appreciate that the counter-intuitive step ofmoving away from the essentially symmetrical proximal support arm pivotand proximal force transmission pivot arrangement of the prior artactually allows one to produce a more symmetrical variation insupporting torque to better match load weight torque.

The invention in its fourth aspect provides a method of designing asupport system. The inventors have appreciated that it is possible toprovide an aesthetically pleasing support system which does not requirea complicated arrangement to match its variations in torque caused by aload on the system as it moves through its range of movement by carefulselection of the dimensions and geometry of that system. Preferredembodiments of the present invention will now be described, by way ofnon-limiting example only, with reference to the attached figures. Thefigures are only for the purposes of explaining and illustratingpreferred embodiments of the invention and are not to be construed aslimiting the claims. The skilled man will readily and easily envisagealternative embodiments of the invention in its various aspects.

In the figures:

FIG. 1 is a perspective view of a support device embodying the presentinvention;

FIG. 2 is a side view of the support device of FIG. 1;

FIG. 3 is a top view of the support device of FIG. 1;

FIG. 4 is a partially exploded view of the support device of FIGS. 1 to3;

FIG. 5 is an exploded view of the upper arm of the support device ofFIGS. 1 to 4;

FIG. 6 is a perspective view of the mounting and movement head of thedevice of FIGS. 1 to 5;

FIG. 7 is a partially exploded view of portions of the mounting andmovement head of FIG. 6;

FIG. 8 is an exploded view of the upper end of the upper arm and themounting and movement head of FIGS. 1 to 6;

FIG. 9 is a cross-sectional view of aspects of the mounting and movementhead along section IX-IX in FIG. 2;

FIGS. 10 a and 10 b are cross-sectional views along part of section X-Xin FIG. 3 illustrating adjustment of the mounting and movement head in afirst plane;

FIGS. 11 a to 11 c are top views of the mounting and movement headillustrating adjustment of the mounting and movement head in a secondplane orthogonal to the plane of the section of FIGS. 10 a and 10 b;

FIGS. 12 a to 12 c are cross-sectional views along part of section X-Xof FIG. 3 which illustrate the invention in its second aspect as theupper support arm pivots;

FIGS. 13 a to 13 g are schematic views of the geometric relationshipbetween the different components of the device of FIG. 1 and whereinFIG. 13 a is an exploded side view of the arm 4, FIG. 13 b is a sidecross-sectional view through the mounting head, FIG. 13 c is a sidecross-sectional view through the mid-joint 31, FIG. 13 d illustrates thegeometry at the proximal end of the support arm, FIG. 13 e illustratesthe geometry of the support arm and its pivots, and FIG. 13 gillustrates the geometry at the distal end of the support arm;

FIGS. 14 and 15 illustrate the variation in torque created about thepivot on the bottom end of the upper arm of FIGS. 1 to 12 by the weightof, for example, a monitor mounted at its upper end, as the support armpivots about that pivot at its bottom end;

FIGS. 16 to 18 illustrate how the torque of FIGS. 13 and 14 is opposedin known support device arrangements;

FIGS. 19 a to 19 c are cross-sectional views similar to those of FIGS.12 a to 12 c illustrating the invention in its third aspect;

FIGS. 20 and 21 illustrate how the torque created at the pivot by theweight of a load on the lower end of the upper support arm is opposed inthe arrangement of FIGS. 1 to 12, and 18;

FIG. 22 is a schematic side view of a further embodiment of a supportsystem in accordance with the invention;

FIG. 23 shows the support system of FIG. 22 from the front; and

FIG. 24 is a schematic side cross-sectional view of the devices of FIGS.22 and 23.

Referring to FIGS. 1 to 3, a support device 1 includes a table securingelement 2, a lower arm 3, upper arm 4, monitor mounting head and pivot5, and a monitor plate 6 for securing to the back of a monitor to besupported (not shown). The table securing element 2 has a screw or clamparrangement for removably securing the element 2 to a table or othersurface and an upstanding pin 7 received within a corresponding hole 8in the end of the lower arm 3 such that the lower arm 3 can rotate abouta vertical Y′ axis (see FIG. 1) relative to the table securing element2. The lower arm 3 then has a hole or female coupling 9 at its upper endto receive a pin or male coupling 10 at the bottom end of the upper arm4. The upper arm 4 can rotate about a vertical axis Y″ (see FIG. 1)relative to the lower arm 3 by virtue of this pin and hole engagement.

Referring to FIG. 1, the lower arm 3 can rotate relative to the tablesecuring element 2 about a vertical axis Y′, the upper arm 4 can rotaterelative to the lower arm 3 about a vertical axis Y″ and a horizontalaxis X″, and (as discussed in more detail below) the mounting head 5 canrotate relative to the distal end of the upper support arm 4 about twoorthogonal axes (one substantially horizontal axis X′″ and the othersubstantially vertical axis Y′″). The monitor supporting head 5 can alsorotate about a horizontal axis Z′″ orthogonal to the X′″ and Y′″ axes.

Referring to FIGS. 5 to 8, the mounting head 5 comprises a movementjoint hoop 11 with a fixing portion 12 for slidable engagement with themonitor supporting plate 6, and an elongate curved member, arc or hoopsegment 13 of substantially circular cross-section. A motion joint 14with an internal circular bearing surface 15 corresponding to thecircumference of the curved member 13 is positioned on the curved member13 and can move along the hoop segment or curved member 13 and rotatearound the hoop segment. The motion joint 14 is a two-part plasticsmoulding. The plastics moulding is held between two projecting portions16 at the distal end of the upper support arm 4. Slotted screws 17 applypressure to the outside of each side of the moulding via rectangularnuts and Belleville washers 18 so that the motion joint is frictionallyengaged on the hoop.

The projecting arms 16 can rotate relative to the motion joint 14 suchthat the support arm can rotate about horizontal axis X′″. Projectingportions 60 on the inside of the upper arm projections 16 engage a track61 on the motion joint 14 to allow this relative rotation about axisX′″.

Referring to FIG. 5, the support device 1 includes movement joint hoop11, distal front link pivot pin 19, proximal front link pivot pin 42,motion joint moulding left half 20, motion joint adjustment screws 17,Belleville washers 18, front link 21, thin hex nut 22, mid joint buttonscrews 23, upper arm casting left half 24, spring slider moulding lefthalf 25, friction pad 26, anti-finger trap moulding 27, power link 28,mid joint pivot pin 29, force adjustment screw 30, mid joint 31, steelwasher 32, spring slider moulding right half 34, compression spring 35,head screw 36, upper arm casting right half 37, rectangular nuts 38,motion joint moulding right half 39, spring nut plate 40 and cablemanagement clip 41.

As illustrated in FIGS. 10 a and 10 b, the motion joint 14 can moverelative to the curved member 13. In this application we will usuallyrefer to movement of the motion joint along the hoop or hoop segment.This expression refers to relative movement in a direction along thecurvature of the curved member 13 and includes movement of the motionjoint with the hoop remaining still, movement of the hoop with themotion joint remaining still and movement of both the motion joint andhoop.

In a particularly preferred embodiment of the invention, the curvedmember 13 lies on the circumference of a circle whose centre lies at ornear the centre of gravity of the monitor or other element beingsupported on the mounting head. This reduces the magnitude of thefrictional force which the bearing surfaces 15 of the motion joint mustapply to the surface of the curved member 13 in order to hold itsposition on the hoop. As illustrated in FIGS. 11 a to 11 c, the motionjoint 14 can also rotate relative to the curved member 13 and acombination of the movement along and about the curved member 13 meansthat, for example, a monitor (not shown) on the mounting head 5, can berotated about orthogonal X′″ and Y′″ axes. In this application weusually refer to rotation of the motion joint about the hoop. Thisexpression refers to relative rotation about a curved axis running downthe middle of the curved member 13 and includes rotation of the motionjoint with the hoop remaining still, rotation of the hoop with themotion joint remaining still and rotation of both the motion joint andhoop.

The mount fixing portion 12 is held in a turntable like portion of themonitor supporting plate 6 such that the monitor supporting plate 6 canrotate relative to the mount fixing portion 12 about axis Z″ (see FIG.1).

The upper support arm 4 is a two-part metal casting whose two halves 24,37 are held together by a screw and nut coupling 36, 22 towards thedistal end of the upper support arm and a pair of proximal mid-jointbutton screws 23 which each pass through a pair of holes in the upperend of the mid joint 31 and engage opposite ends of the mid joint pivotpin 29 so that the upper support arm 4 can pivot about that mid jointpivot pin 29 and hence about horizontal axis X″ (see FIG. 1). The distalend of each half of the upper support end casing forms one half 16 of aU-shaped motion joint fixing portion so that together the two halves ofthe casting capture the motion joint 14 as described above (see FIGS. 8and 9). An upper support arm front link 21 is mounted at its distal endon the distal front link pivot 19 held between the two halves 20, 39 ofthe motion joint 14 and at its proximal end on a proximal front linkpivot pin 42 pivotally mounted on the distal end of a slidingcarriageway or spring slider 43 supported within the upper arm casing.The spring slider 43 is a two-part moulding 25, 34 and the proximalfront link pivot pin 42 is held between the distal ends of the twohalves to support the front link 21. When the device is assembled, theslider 43 moves along the longitudinal axis L of the support arm 4without a component of movement perpendicular thereto. The describedembodiments have the spring slider 43 inside the support arm; it couldalso be arranged around or alongside the upper support arm 4 providedthat it moves along or parallel to the longitudinal axis L of the uppersupport arm 4 with no significant component of movement perpendicularthereto.

The spring slider 43 has a compression spring 35 (not shown in FIGS. 12a to 12 c) inside it which engages at its distal end with a spring nutplate 40 mounted on the distal end of a force adjusting screw 30. Atinitial set up or final manufacture of the support device 1, the forceadjustment screw is set to define a particular separation between thespring nut plate 40 and the proximal end of the spring slider 43. Thisdefines the length of the space for the compression spring 35 and hencedetermines the force supplied by the spring 35. The force adjustingscrew 30 can adjust the position of the spring nut plate 40 within thespring slider moulding and thereby increase or decrease the length ofthe compression spring and hence, respectively, decrease or increase theforce that spring will apply to the spring slider and spring nut plate,and hence to the rear power link 28 pivotally connected to the proximalend of the spring slider 43 against which the proximal end of the spring35 acts.

The rear power link 28 is arranged between the proximal end of thespring slider 43 and the mid-joint 31 so as to transmit the force fromthe compression spring 35 to the mid-joint 31. The rear power link 28 isconnected to the spring slider 43 at the rear power link's distal end bya distal rear link pivot pin 44 held between the two moulding halves 25,34 of the spring slider 43 and is connected to the mid-joint 31 by aproximal rear link pivot pin 45 held between two upstanding portions 46of the U-shaped mid-joint 31. The rear power link proximal pivot 45 islocated on the mid-joint below the upper arm pivot point 29 and at aposition forward or distal from the vertical axis passing through thatsupport arm pivot point 29.

As will be discussed in more detail below, the combination of thesupport arm outer casing 47 pivotally coupled at its proximal end to themid-joint 31 and at its distal end to the motion joint 14, combined withthe internal slider 43 coupled at its distal end via the front link 21and at its proximal end via the rear power link 28 means that a monitorsupported on the mounting head remains in substantially the same planeas the upper support arm 4 pivots about the mid-joint 31 in the mannershown in FIGS. 12 a, 12 b and 12 c.

Referring to FIGS. 12 a to 12 c, as the upper support arm pivots aboutthe mid-joint pivot pin in direction A from, for example, the positionshown in FIG. 12 a to the position shown in FIG. 12 b (or, for example,the position shown in FIG. 12 b to the position in FIG. 12 c), the rearpower link 28 pushes the slider 43 in the support arm casing 47 towardsthe motion joint 14. This then causes the front link 21 to push itspivot point on the motion joint forward. As the distal front link pivotpin 19 is located on the motion joint 14 at a point below the pivot oraxis of rotation X′″ between the motion joint 14 and the support armouter casing 47, this causes the motion joint 14 to rotate in directionB relative to the support arm casing 47 and thereby reduce or preventtilting of the monitor relative to its original plane. If there were nomovement of the motion joint in direction B relative to the supportcasing, a monitor held on the mounting head would tilt in direction C asthe support arm was rotated in direction A.

Slider 43 can slide freely along support arm casing 47, along the centreor longitudinal axis L of the bar or force adjustment screw 30. In theillustrated embodiment, the slider 43 is inside the support arm casing47 but it is also possible to have the slider 43 and associated linksand pivots arranged outside and around the casing 47. As the uppersupport arm moves through its range of motion (for example, in directionA from about 40° above the horizontal, as shown in FIG. 2 a to about 40°below the horizontal as shown in FIG. 12 c), slider 43 slides along andrelative to the arm casing 47 at a certain rate (i.e. distance along armcasing per degree of rotation). This sliding rate is defined by thegeometry of the rear power link 28, the position of the proximal rearlink pivot pin 45 relative to the mid-joint pivot pin 29, and theposition of distal rear link pivot 44 relative to the centrelongitudinal axis of the bar 30. The rotation in direction B is at adefined rate (i.e. angle of rotation per measure of distance moved byslider 43 along the central axis of the arm). This rate of rotation isdefined by the geometry of the front link 21, the front link distalpivot 19, the pivot X′″ (see FIG. 1) and the front link proximal pivot42 relative to the centre axis L.

Referring to FIGS. 13 a to 13 g, the distances or values d, z, e, g, I,n, o, offset, m, j. In length and k, d—distance between mid-joint pivot29 and proximal force transmission link pivot 45; z—angle to vertical ofthe straight line between mid-joint pivot 29 and proximal forcetransmission link pivot 45; e—distance along perpendicular line from(longitudinal axis of support arm) to distal pivot 44 of proximal link28; g—length of proximal force transmission link 28 between itsrespective pivots; I—distance between proximal and distal support armpivots 29, X′″; n—component along support arm longitudinal axis betweenproximal pivot 42 of distal link 21 and distal pivot 44 of proximal link28; o—distance along perpendicular line from (longitudinal axis ofsupport arm) to proximal pivot 42 of distal link 21; offset—theperpendicular distance of the pivot point of the motion head from thelongitudinal axis; m—the parallel distance between the pivot point ofthe motion head and the pivot point 19; j—length of distal link 21between its respective pivots 19, 42; In length—free spring length (i.e.length of unloaded spring); K—spring constant, are all constant as theupper support arm 4 pivots about pivot pin 29; the values of x, y, a,Spring D, p, f, B1, B2, angle C and (not shown in FIGS. 13 a to 13 g)Spring force W, x—angle between longitudinal axis of arm and vertical;y—angle between longitudinal axis of arm and line between the pivots ofthe force transmission link 28; a—distance along longitudinal axis ofarm between link distal pivot 44 and mid-joint pivot 29; SpringD—stressed spring length; p—distance along longitudinal axis of armbetween distal link proximal pivot 44 and mounting head pivot X′″;f—parallel distance between pivot 42 and cross-section between centreline of motion joint surface 15 and vertical line motion head; B1—anglebetween longitudinal axis of arm and line between mounting head pivotX′″ and distal link proximal pivot 43; B2—angle between line betweenmounting head pivot X′″ and distal link proximal pivot 43, and linebetween mounting head pivot X′″ and distal link distal pivot 19; T—tiltangle (angle between line between vertical and line between mountinghead pivot X′″ and distal link distal pivot 19; angle C—angle betweenline between mounting head pivot X′″ and distal link distal pivot 19,and line between the pivots 19, 42 of the distal link 21), however varyas the arm 47 rotates or pivots about pivot 29, thorough angle x.

As the slider 43 holds distal rear link pivot 44 and proximal front linkpivot 42 a fixed distance or apart, pivots 42 and 44 will move at thesame rate which, as discussed above, is defined by the geometry of therear power link 28, proximal rear link pivot 45, mid-joint pivot 29,distal rear link pivot 44 and the centre line through the slider 43,support arm casing 47 and axis L of the bar 30 (along which all threemove relative to each other).

As pivot 42 moves forward at the defined rate set by the geometry of thevarious elements at the proximal end of the slider 43 and support armcasing 47, front link 21 converts this sliding action to a rotation indirect B about axis X′″ (see FIGS. 1 and 12 a to 12 c).

As the arm 4 rotates, the aim is to keep angle T (see FIGS. 13 e and 13f) constant or almost constant so that, for example, a monitor on themounting head is at the same angle as the arm is rotated. In practicethe angle T is selected so that the monitor tilts 5 degrees upwards asthis allows for any tolerances/variations in the assembly of the supportarm. Experience also suggests that the market perception of a monitorarm is better if the screen points up slightly rather than points down(as this gives the impression of drooping).

The inter-relationship between the various parameters illustrated inFIGS. 13 a to 13 g is defined by the following equations;

$\begin{matrix}{p = {l - n - a}} & (1) \\{f = \sqrt{P^{2} + \left( {o - {offset}} \right)^{2}}} & (2) \\{{B\; 1} = {a\;{\tan\left( \frac{o - {offset}}{p} \right)}}} & (3) \\{{\cos\left( {B\; 2} \right)} = \frac{m^{2} + f^{2} - J^{2}}{2{mf}}} & (4) \\{T = {x - {B\; 1} - {B\; 2}}} & (5) \\{{\cos\; C} = \frac{m^{2} + J^{2} - f^{2}}{2{mj}}} & (6)\end{matrix}$

As shown in, for example, FIGS. 1, 12 a, 12 b and 12 c, in order toraise and/or lower a monitor (not shown) fixed to the mounting head 14relative to the lower arm 3 and hence the table surface on which thesupport device 1 is mounted, the upper support arm 4 can be rotated fromits highest position (see FIG. 12 a), approximately 45 degrees above thehorizontal down to its lowest position (see FIG. 11 c), approximately 45degrees below the horizontal. The spring 35 inside the support arm 4acts on the mid-joint 31 via the rear link 28 to produce a torque whichcounter-acts the torque produced by the weight of the monitor.

As can be seen from FIG. 14, the distance of the monitor from its centreof gravity to the mid-joint pivot P, is at its greatest when the uppersupport arm is horizontal (FIG. 14 b) and at its lowest when the monitoris in either its uppermost (FIG. 14 a) or lowermost (FIG. 14 c)positions.

This means that (as shown in FIG. 15) the torque at the mid joint pivot29 (P in FIGS. 14 and 16) created by the monitor weight is at a maximumwhen the arm angle to the horizontal is 0° and at a minimum at the endsof its range of movement which are +45° and −45° in the illustratedexample. The graph of FIG. 15 is an illustration of the magnitude of thetorque at P (i.e. pivot point 29) created by a monitor weight whichassumes a monitor weight of 40N, an arm length of 265 mm and a range ofmovement of +/−45° from the horizontal.

The known arrangements (see FIG. 16) for opposing the torque created atthe pivot point 29 by the load at the distal end of the support arm usea spring force G created by either a mechanical spring or gas springinside the upper support arm 4. This spring force G is transmitted via arear power link 51 of length f which acts through proximal rear linkpivot point 52 at a distance d vertically below the main support armpivot point P (or 29). The torque T at P generated by the spring force Gis the product of the force S in the rear link 51 and the distance d.Force S is equal to the component of spring force G along the directionof the rear power link.

Referring to FIG. 17, if the spring force G is constant and the range ofmovement of the support arm is +/−45° from the horizontal, then thevariation in T is as shown in FIG. 17 by the constant force line 65. Thetorque T varies as the support arm pivots because the component of thespring force G along the direction of the rear power link 51 varies asthis pivots relative to the upper support and the direction of thespring force G. As can be seen in FIG. 17, the torque created by theconstant spring force in the known arrangement of FIG. 16 does not varyin the same way as the torque created by the weight of the load W (line66 in graph). In particular, the peak weight opposing torque 62 (i.e.the torque produced by the spring force G) is not at the same positionas the peak torque created by the load weight. Furthermore, if thespring force is created by a mechanical spring such as a compressionspring, the differences are even greater (see FIG. 18 wherein thevariation in torque from a compression spring is line 67)). This isbecause the magnitude of the spring force G varies as the spring iscompressed to varying degrees as the upper support arm rotates.

In the embodiment of the invention shown in FIGS. 1 to 11 and 18, thetorque produced by the weight of the monitor (see FIGS. 19 and 20) isopposed by a torque which is the product of the spring force created bythe compression spring 35 in the rear power link 28 and theperpendicular distance e between the line of that force and the proximalpower link pivot 45.

Referring to FIGS. 13 a to 13 g and 20 a to 20 c:

$\begin{matrix}{{\sin\; y} = \frac{{d\;{\sin\left( {x + \overset{\_}{z}} \right)}} - e}{g}} & (7) \\{a = {{g\;\cos\; y} - {d\;{\cos\left( {x + \overset{\_}{z}} \right)}}}} & (8) \\{{{Spring}\; D} = {{setting}_{n} + {block} - a}} & (9) \\{{{Spring}\mspace{14mu}{force}} = {\left( {{{In}\mspace{14mu}{length}} - {{Spring}\mspace{14mu} D}} \right) \cdot K}} & (10)\end{matrix}$

-   -   where: In length=unstressed spring length (i.e. free/initial        spring length)    -   Spring D=stressed spring length (this is an instantaneous value        as can be taken at any point in the movement)    -   K=Spring constant

The torque ω at the pivot 29 resulting from that spring force is thengiven by

$\begin{matrix}{\omega = \frac{{Spring}\mspace{14mu}{{force} \cdot \cos}\;{y \cdot {\cos\left( {{90{^\circ}} - x - \overset{\_}{z} + y} \right)} \cdot d}}{l \cdot \sin \cdot x}} & (11)\end{matrix}$

The dimensions of the support arm and its associated elements, (i.e.d—distance between mid-joint pivot 29 and proximal force transmissionlink pivot 45; z—angle to vertical of the straight line betweenmid-joint pivot 29 and proximal force transmission link pivot 45;e—distance along perpendicular line from longitudinal axis of supportarm to distal pivot 44 of proximal link 28; g—length of proximal forcetransmission link 28 between its respective pivots; I—distance betweenproximal and distal support arm pivots 29, X′″; n—component alongsupport arm longitudinal axis between proximal pivot 42 of distal link21 and distal pivot 44 of proximal link 28; o—distance alongperpendicular line from longitudinal axis of support arm to proximalpivot 42 of distal link 21; offset—the perpendicular distance of thepivot point of the motion head from the longitudinal axis; m—theparallel distance between the pivot point of the motion head and thepivot point 19; j—length of distal link 21 between its respective pivots19, 42′; In length—free spring length (i.e. length of unloaded spring);K—spring constant) are selected so as to try and best match the twinobjectives of keeping angle T roughly constant through the range ofmotion of the support arm, and of closely matching the torques about thepivot 49 exerted by the weight of a load such as a monitor on themounting head 14 and that exerted by the spring force through the rangeof motion of the support arm. Friction acts at two main points: betweenthe slider 43 and outer casing 47 and also at the mid-joint 29.Increased spring load leads to increased friction but it is notnecessary to precisely determine the exact friction levels as fricationis used as an aid to provide a degree of tolerances to the functioningsystem.

The inventors of the subject invention have appreciated that it ispossible to match the torque created by the spring force of a springwithin the support arm to the torque created by a load weight withoutthe use of a cam such as used in the prior art by careful selection ofthe arm geometry and that a support arm with a slider moveable along itscentre axis with rear and front link pivots combined with the freedom tolocate the rear link proximal pivot 45 of a point other than verticallybelow the support arm proximal pivot 29 allows for the selection of ageometry loading to a sufficiently close match. The inventors haveappreciated that frictional forces means that a perfect match is notnecessary and that the standard construction with a rear link powerpivot vertically underneath the main support arm proximal pivot wassub-optimal.

The selection of the support arm geometry is done by a targetedgraphical method. For a live load the torque about pivot 29 isdetermined for different support arm positions and plotted as a graphsimilar to that of FIG. 15.

The counter-balancing torque is given by equation 11. Values for each ofthe relevant constant (i.e. constant as the arm rotates) parameters areselected iteratively limited by the range of values of each which arepossible and appropriate for the arm's function and aesthetics. Each setof those selected values is input into equations 7 to 11 for a series ofdifferent values of the angle x (and hence of other variable angles andlengths which vary as the arm rotates) to generate a graph similar tothat of FIG. 21. The fixed or constant values (i.e. d—distance betweenmid-joint pivot 29 and proximal force transmission link pivot 45;z—angle to vertical of the straight line between mid-joint pivot 29 andproximal force transmission link pivot 45; e—distance alongperpendicular line from longitudinal axis of support arm to distal pivot44 of proximal link 28; g—length of proximal force transmission link 28between its respective pivots; I—distance between proximal and distalsupport arm pivots 29, X′″; n—component along support arm longitudinalaxis between proximal pivot 42 of distal link 21 and distal pivot 44 ofproximal link 28; o—distance along perpendicular line from longitudinalaxis of support arm to proximal pivot 42 of distal link 21; offset—theperpendicular distance of the pivot point of the motion head from thelongitudinal axis; m—the parallel distance between the pivot point ofthe motion head and the pivot point 19; j—length of distal link 21between its respective pivots 19, 42′; In length—free spring length(i.e. length of unloaded spring); K—spring constant) are then variediteratively until the line on the graph of the torque generated by thespring force of FIG. 21 closely matches the line on the graph of thetorque generated by the load of FIG. 15.

The illustrated embodiment of the invention has a force adjustment screw30 which can pre-stress the spring 30 which can pre-stress the spring 35to a different extent and thereby also affect the torque about pivot 29resulting from the spring force. The matching exercise described aboveis therefore repeated for a number (say 4) of different pre-stresseswhich would correspond to different monitor weights or loads as a checkthat a selected geometry can also match different loads and degrees ofappropriate pre-stressing of the spring 35.

Once a geometry which closely matches torque is achieved, equations 1 to6 are used to plot a graph of T and the same iterative process is usedto find geometry values for which T remains roughly constant during therange of movement of the arm. This may require some modification of thevalues determined by the first stage of iteration so it may be necessaryto repeat that first process of matching torque lines or a graph until ageometry which best matches the twin requirements of constant T andmatching torque w is achieved.

As shown in FIGS. 19 a to 19 c, in the described embodiment, theproximal rear power link pivot pin 44 of the described embodiment of theinvention is located forward (or distal) from the axis W (see FIG. 19 b)through the mid-joint pivot 29 which is orthogonal to the longitudinalaxis of the upper support arm at the mid point of range of movement ofthe upper support arm; i.e. the proximal rear link pivot 44 is forwardof a vertical axis through the mid-joint pivot 29 when the upper supportarm can move between +/−45° to the horizontal. The inventors havedetermined that locating the rear power link pivot pin 44 forward orback from the vertical through the mid-joint pivot 29 allows for abetter match of the torque exerted by the spring force about the pivot29 to the torque exerted by the weight of a load on the mounting head 14as the support arm moves through its range of motion.

As illustrated in FIGS. 20 and 21 where line 68 illustrates thevariation in torque created about the pivot pin 29 by the compressionspring 35 acting via the rear power link 28, this position of theproximal rear power link pivot pin 4 moves the peak torque aboutmid-joint pivot 29 created by the spring 35 acting through the rearpower link 28. Careful selection of the geometry and/or dimensions ofthe element (and their relative geometry and dimensions) making up theproximal end of the upper support arm 4 (including the rear link 28;pivots 29, 44, 45), the spring properties and the load weight allow oneto move the position of peak opposing torque 64 (see FIG. 21) to aposition closer to the position of the peak load weight torque of line66.

The placing of the proximal pivot 45 for the rear link at a positionforward or distal from the vertical line through the proximal supportarm pivot 29 (i.e. forward or distal from the line or axis along whichgravity acts means that the perpendicular distance e varies in a mannerwhich is closer to the variation in the torque caused by the weight ofthe monitor than is the case in the known arrangements which have therear link pivot point in line with a vertical line through the proximalsupport arm pivot.

Referring to FIGS. 19 a to 19 c, as the support arm 4 rotates from itsuppermost position (see FIG. 19 a), through the mid-position (see FIG.19 b) down to its lowermost position (19 c), the rear power link 28progressively compresses the spring 35 by pushing it against the fixedspring nut plate 40. This means that the force provided by the spring 35progressively increases as the support arm 4 is lowered in a mannersimilar to that discussed above in connection with FIG. 18.

A further embodiment is shown in FIGS. 22-24 of the drawings.

Whilst it is usual to mount the display device on a support arm, thereare some situations in which it may be desirable for the display deviceto be stored flat against, or in a recess so that it flush with, asurface such as a wall or table-top when it is out of use, but to bemovable away from the surface to a more comfortable position for viewingwhen in use. A support system utilising the invention intended for thesecircumstance is shown schematically in FIGS. 22 to 24.

The embodiment of FIGS. 22 to 24 differs from those described above inthat the support arm and hoop element are replaced by a single curvedarm 100 which is of circular cross-section along its entire operativelength. The curved arm 100 cooperates with a motion joint 102 generallysimilar to motion joint 14 described above.

The internal features of motion joint 102, in particular, the internalbearing surface which engages the external surface of the curved arm100, are the same as those of motion joint 14, but the external casing104 of the motion joint 102 is designed to allow it to be mountedsecurely in a through opening formed in, as shown in the drawings, agenerally horizontal surface such as a tabletop 106. For example, theouter casing 104 may be formed in two parts, each provided with anoutwardly-extending annular flange, so that when the two parts of thecasing 104 are secured together, the margin of the tabletop 106 aroundthe through opening is trapped between the flanges to secure the casing104 in the through opening. Alternatively, the casing 104 may be securedby other means such as gluing.

Although FIGS. 22 to 24 show the support system being used to mount adisplay device 101 relative to a generally horizontal surface, it willbe understood that a similar arrangement may be used in respect ofgenerally vertical surfaces such as walls or, indeed, in relation toinclined surfaces.

The display device 101 is secured to the curved arm 100 by means of asuitable mounting plate 108. Whilst this may serve simply to hold thedisplay device 101 on the end of the curved arm 100 in a fixed position,the mounting plate 108 preferably includes a bearing 110 so that thedisplay device 101 can be rotated at will about the end of thecircular-section curved arm 100. This not only allows fine adjustment ofthe viewing position of the display device 101 in use but alsofacilitates stowing of the display device 101 neatly against thetabletop 106 or in a recess, where one is provided, when it is no longerneeded.

The end of the curved arm 100 remote from the display device 101 isprovided with an end cap 112 of larger diameter than the curved arm 100which acts as a stop to prevent the curved arm 100 being drawn all theway through and removed from the motion joint 102.

In use, the curved arm 100 can be moved through the motion joint 102,overcoming the friction exerted by the internal bearing surface, untilthe display device 101 is a suitable distance from the surface of thetabletop 106. The frictional engagement of the internal bearing surfacewith the cylindrical surface of the curved arm 100 will then prevent thearm 100 sliding back through the motion joint 102. The position andorientation of the display device can then be adjusted further either byrotation of the curved arm 100 about its axis within the internalbearing surface of the motion joint 102 or by rotation mounting plate108 of the display device 101 about the central axis of the end of thecurved arm 100, or both.

When the display device is no longer needed, it can simply be returnedto its original position against, or housed in a recess formed in, thetabletop 106. The curved arm 100 can be hollow so that cables can be fedthrough it.

The invention claimed is:
 1. A support system for pivotably supporting aload comprising: a curved member having a circular cross section; and amotion joint slidable and rotatable relative to the curved member,wherein an outer surface of the curved member matches a bearing surfaceof the motion joint, wherein the motion joint and the curved member arerotatable relative to each other about a first axis extending throughthe curved member perpendicular to the circular cross section, andwherein the motion joint and the curved member are rotatable relative toeach other about a second axis perpendicular to the first axis, thesecond axis located at a center of curvature of the curved member.
 2. Asupport system according to claim 1 wherein the curved member isprovided with a mount for securing a load to the curved member.
 3. Asupport system according to claim 2 wherein the mount comprises amounting plate and a joint rotatably joining the mounting plate and thecurved member.
 4. A support system according to claim 1, wherein: thecurvature of the curved member relative to the second axis is defined bya portion of the circumference of a circle; and the motion joint furtherincludes a support arm-mount, wherein a support arm mounted on thesupport arm mount is slidable along and rotatable about the first axisof the curved member.
 5. A system according to claim 4 wherein thesupport arm is pivotally connected to the motion joint.
 6. A systemaccording to claim 5 further comprising a display device coupled to thecurved member, the display device having a center of gravity at or nearthe second axis.
 7. A support system according to claim 1 having stopmeans provided at at least one end of the curved member to preventcomplete withdrawal of the curved member through the motion joint.
 8. Asupport system comprising: a motion joint having an internal bearingsurface; and an elongate curved member provided with at least oneaxially-extending, at least part cylindrical operative surface forengaging with the internal bearing surface of the motion joint; theinternal bearing surface of the motion joint being at least partcylindrical and being adapted to frictionally engage the curved memberor each operative surface of the curved member so as to allow a loadsecured to the curved member to be supported in a selected longitudinalposition of the curved member relative to the motion joint; the curvedmember being rotatable about a first axis of the operative surfacewithin the internal bearing surface to further adjust the positionand/or orientation of the load relative to the motion joint, and thecurved member being rotatable relative to the internal bearing surfaceabout a second axis perpendicular to the first axis.
 9. A support systemaccording to claim 8 wherein the motion joint is provided with means forsecuring the motion joint in a through opening formed in a wall orsurface so that the curved member extends through said wall or surface,in use.
 10. A support system according to claim 9 further comprising thewall or surface, wherein the means for securing the motion joint issecured in the wall or surface, and wherein the curved member ismoveable through the motion joint and wall or surface.
 11. A supportsystem for pivotably supporting a load comprising: a motion jointcomprising a casing shaped and dimensioned to be received through anopening formed in a support member, wherein the motion joint comprisesan internal bearing surface; an elongate curved member having a circularcross section and comprising an outer surface frictionally engaging theinternal bearing surface of the motion joint, wherein the curved memberis moveable through and relative to the motion joint, wherein the motionjoint and the curved member are rotatable relative to each other about afirst axis extending through the curved member perpendicular to thecircular cross section, and wherein the motion joint and the curvedmember are rotatable relative to each other about a second axisperpendicular to the first axis, the second axis located at a center ofcurvature of the curved member; a mounting plate rotatably joined to afirst end of the curved member on first side of the motion joint,wherein the mounting plate is rotatable relative to the first end of thecurved member about at least one axis, and wherein the mounting plate isadapted to support a display device; and a stop member joined to asecond end of the curved member opposite the first end and on anopposite second side of the motion joint, the stop member sized toprevent complete withdrawal of the curved member through the motionjoint.
 12. A support system according to claim 11 further comprising thesupport member having the opening, wherein the casing is disposed in theopening of the support member, and wherein the curved member is moveablethrough the motion joint and the support member.
 13. A support systemaccording to claim 12 wherein the support member has a horizontalsurface.
 14. A support system according to claim 12 wherein the supportmember has a vertical surface.
 15. A support system according to claim12 wherein the casing comprises at least one flange engaging the supportmember.
 16. A support system according to claim 11 further comprisingthe display device, wherein the display device is coupled to themounting plate.